Automated mass mailing machines for processing large quantities of documents have been in use for many years. Such machines typically include a folder which folds sheets into envelope size, an inserter track that receives and processes the folded sheets along with other inserts, and means for inserting the folded sheets into envelopes.
The inserting means can comprise an envelope opening means that includes a plow member positioned adjacent the inserter track. As the envelopes are moved down the inserter track, they contact the plow member whereby the plow member is interposed between the rear surface of a moving envelope and the envelope flap to force the flap into a fully opened position. The opened envelope is then passed to an inserting station where the folded sheets and inserts are automatically inserted into the envelope. Thereafter, the stuffed envelope is sealed for mailing.
One problem associated with such envelope opening devices is the sticking of envelopes which occurs when the mailing machine is operated at a high speed and the plow member does not properly separate the envelope flap from the rear surface of an envelope.
Such sticking is a common problem because of the way envelopes are made and stored. Envelopes are stacked tightly together with the envelope flap folded against the rear surface of the envelope. This eliminates any natural spacing between the envelope and its flap caused by the resiliency of the creased paper. In addition, the flaps are usually treated with a moisture sensitive adhesive for sealing. Even when the envelopes are not subjected to moisture before processing, this adhesive often causes the flaps to adhere slightly against the envelopes.
Several attempts have been made to provide an apparatus that separates envelope flaps from envelopes so that the plow member can readily be inserted. For example, U.S. Pat. No. 3,583,124 to Morrison discloses an envelope flap opening apparatus that includes a suction cup mounted on a rotatable shaft and positioned alongside an envelope conveyer means. After the suction cup makes contact with the flap of an envelope traveling on the conveyer, a vacuum is applied to the suction cup. The suction cup then engages the envelope flap and rotates about the axis of the rotatable shaft away from the plane of the conveying means, thereby partially opening the flap. A plow member assembly rotates in the direction of the flap until a vertical head portion of the plow member contacts the leading edge of the partially opened flap. The plow member then forces the flap to a fully opened position.
The envelope flap opening apparatus described in the Morrison patent requires that the conveying means and the envelope are stopped for a dwell period in the machine cycle. The dwell period is necessary to permit the suction cup to engage the envelope flap; to rotate the suction cup and the envelope flap adhering thereto away from the plane of the conveying means; and to force the flap into a fully opened position. Unfortunately, the dwell period increases production time and lowers the efficiency of the inserting apparatus.
U.S. Pat. No. 4,318,265 to Orsinger et al. discloses a envelope flap opening apparatus that includes a stationary plow member and a rotatable, slidable suction cup. The suction cup is mounted on a shaft that moves alongside an envelope conveyor. When the suction cup engages the envelope flap, the shaft rotates the suction cup to partially open the flap. The envelope and the engaged suction cup advance together until the partially opened flap contacts the stationary plow member.
While the envelope flap opening apparatus described in the Orsinger et al. patent does reduce the dwell period of the device, it has several drawbacks. The number of moving parts makes this device particularly susceptible to breakdown, which is a common problem in the operation of such high speed devices. In addition, while faster than the Morrison et al. apparatus, the Orsinger et al. apparatus operates at a limited speed because the suction cup must sealingly engage the envelope flap. If the operating speeds are too high, machine vibrations can interfere with the efficient operation of the apparatus.
Thus, an envelope flap opener is needed which is capable of high speed operation, is dependable and is less susceptible to breakdown than currently available machines.